Reverse lens? what's that? and how?

Hi, I read on many macro photography-threads that those pics were taken using reverse lens.

Well, I search what is that on google and found that in SLR world reverse lens is to take the lens out of the camera and put it again but just in the reverse way (with some kind of adapter), my english is not good to explain this very well but you may understand.
First at all, is this correct?

Second, on those threads I mentioned, people use reverse lens with cameras like A610/620 and if I'm not wrong you can't take the lens out of this camera. Am I right? So, how did they use this technique with that kind of camera??